JP7649341B2 - Engine Control Unit - Google Patents

Description

The present invention relates to an engine control device.

Conventionally, engines that perform homogenous charge compression ignition combustion, in which a mixture of fuel and air is compressed and self-ignited, are known (see, for example, Patent Document 1). In the engine described in Patent Document 1, gasoline fuel is injected into the combustion chamber from an injector during the intake stroke or compression stroke, and after the injected gasoline fuel is mixed with the air introduced into the combustion chamber, it self-ignites near the top dead center of compression. In addition, when the engine is started cold, the ignition of the mixture is assisted by a spark plug.

JP 2019-105227 A

However, because the device described in Patent Document 1 uses gasoline fuel that has low ignition properties, even if the mixture is ignited by a spark plug, the flame may not grow sufficiently during cold start, resulting in a misfire.

An engine control device according to one aspect of the present invention includes an engine that is a spark ignition engine having an injector that injects fuel into a combustion chamber and an ignition plug that ignites a mixture of fuel and air in the combustion chamber, a temperature detection unit that detects a coolant temperature of the engine, and a control unit that controls the injector based on the coolant temperature detected by the temperature detection unit. The fuel injected from the injector is at least one of gasoline fuel and reformed fuel obtained by reforming a part of the gasoline fuel into a peroxide. The control unit controls the injector to inject gasoline fuel at a first target injection timing when the coolant temperature detected by the temperature detection unit exceeds a predetermined temperature at the start of the engine, and controls the injector to inject reformed fuel at a second target injection timing that is retarded from the first target injection timing when the coolant temperature detected by the temperature detection unit is equal to or lower than the predetermined temperature , and thereafter controls the injector to inject gasoline fuel at the first target injection timing when ignition by the ignition plug is successful in a predetermined number of combustion cycles.
An engine control device according to another aspect of the present invention includes an engine that is a homogeneous charge compression ignition engine having an injector that injects fuel into a combustion chamber and an ignition plug that ignites a mixture of fuel and air in the combustion chamber, a temperature detection unit that detects a coolant temperature of the engine, and a control unit that controls the injector based on the coolant temperature detected by the temperature detection unit. The fuel injected from the injector is at least one of gasoline fuel and reformed fuel obtained by reforming a part of the gasoline fuel into a peroxide. The control unit controls the injector to inject gasoline fuel at a first target injection time when the cooling water temperature detected by the temperature detection unit exceeds a predetermined temperature, which is the cooling water temperature when the engine is started cold, when the cooling water temperature detected by the temperature detection unit is below the predetermined temperature, controls the injector to inject reformed fuel at a second target injection time that is retarded from the first target injection time, and controls the spark plug to ignite the mixture of reformed fuel and air in the combustion chamber, and thereafter, when ignition by the spark plug is successful after a predetermined number of combustion cycles, controls the injector to inject gasoline fuel at the first target injection time, and controls the spark plug to ignite the mixture of gasoline fuel and air in the combustion chamber.

The present invention can improve the starting performance of the engine when it is started cold.

1 is a diagram showing an example of an internal configuration of an engine of an engine control device according to an embodiment of the present invention; FIG. 2 is a diagram illustrating an example of a fuel supply passage that supplies fuel to an engine of the engine control device according to the embodiment of the present invention. 1 is a block diagram showing an example of a configuration of a main part of an engine control device according to an embodiment of the present invention; FIG. 2 is a diagram for explaining the relationship between the peroxide concentration in a fuel and the octane number and ignition quality. 5 is a diagram for explaining the relationship between the fuel injection timing, the in-cylinder temperature, and the heat release rate. 4 is a diagram for explaining the relationship between the fuel injection timing, the in-cylinder pressure, and the heat release rate. FIG. FIG. 4 is a diagram for explaining injection timing at the time of cold start. 3 is a flowchart showing an example of a start process when the engine control device according to the embodiment of the present invention is applied to a spark ignition engine. 3 is a flowchart showing an example of a start process when the engine control device according to the embodiment of the present invention is applied to a homogenous charge compression ignition engine.

Hereinafter, an embodiment of the present invention will be described with reference to Figures 1 to 9. An engine control device according to an embodiment of the present invention is applied to a spark ignition engine or a homogenous charge compression ignition engine mounted on a vehicle, and performs engine control to improve startability during cold start.

Normal octane gasoline fuel has low ignition properties, and even if the mixture is ignited by a spark plug, there is a risk of misfire during cold start due to the flame not growing sufficiently. Therefore, in this embodiment, the engine control device is configured as follows to improve startability during cold start by using reformed fuel in which part of the gasoline fuel is reformed into peroxide as necessary.

Figure 1 is a diagram showing a schematic diagram of an example of the internal configuration of an engine 1 of an engine control device (hereinafter, device) 100 according to an embodiment of the present invention. As shown in Figure 1, the engine 1 has a cylinder block 3 in which a cylinder 2 is formed, and a cylinder head 4 covering the upper part of the cylinder block 3. The cylinder head 4 is provided with an intake port 5 through which intake air to the engine 1 passes, and an exhaust port 6 through which exhaust air from the engine 1 passes. The intake port 5 is provided with an intake valve 7 that opens and closes the intake port 5, and the exhaust port 6 is provided with an exhaust valve 8 that opens and closes the exhaust port 6. The intake valve 7 and exhaust valve 8 are driven to open and close by a valve mechanism (not shown).

A piston 9 is disposed in each cylinder 2 so as to be able to slide within the cylinder 2, and a combustion chamber 10 is formed facing the piston 9. A throttle valve 12 is provided in an intake passage 11 that communicates with the combustion chamber 10 via an intake port 5. The throttle valve 12 is, for example, a butterfly valve, and adjusts the amount of air (intake amount) drawn into the combustion chamber 10. The opening of the throttle valve 12 (throttle opening) is controlled by an electronic control unit (ECU (Electronic Control Unit)) 50 (Figure 3).

An injector 13 and a spark plug 14 are attached to the cylinder head 4 so as to face the combustion chamber 10. The injector 13 is configured as an in-cylinder fuel injection valve and injects fuel into the combustion chamber 10. The spark plug 14 generates a spark by electrical energy and ignites the mixture of fuel and air in the combustion chamber 10. The fuel injection timing (valve opening timing) of the injector 13, the fuel injection amount (valve opening time), the ignition timing of the spark plug 14, and the on/off of ignition by the spark plug 14 are controlled by the ECU 50 (Figure 3). Although not shown, the engine 1 is also provided with a water temperature sensor 15 (Figure 3) that detects the temperature (water temperature) Tw of the engine cooling water, an outside air temperature sensor 16 (Figure 3) that detects the intake air temperature (outside air temperature) Ta, and the like. Signals indicating the detection results by the water temperature sensor 15 and the outside air temperature sensor 16 are sent to the ECU 50 (Figure 3).

When the intake port 5 is opened, the exhaust port 6 is closed, and the piston 9 moves down, air (fresh air) is drawn into the combustion chamber 10 through the intake port 5 (intake stroke). When the intake port 5 and exhaust port 6 are closed and the piston 9 moves up, the air or mixture in the combustion chamber 10 is compressed, and the pressure in the combustion chamber 10 gradually rises (compression stroke).

In a spark ignition engine, fuel is injected into the combustion chamber 10 from the injector 13 during the intake stroke or compression stroke, and the mixture is ignited by the spark plug 14 near the compression top dead center (TDC), and the fuel in the combustion chamber 10 is burned by flame propagation. This type of combustion is hereinafter referred to as spark ignition (SI) combustion.

In homogenous charge compression ignition engines, fuel is injected into the combustion chamber 10 from the injector 13 during the intake stroke or compression stroke, and when the temperature of the mixture in the combustion chamber 10 rises due to compression, the fuel burns by self-ignition near the compression top dead center (TDC). This type of combustion is referred to below as homogenous charge compression ignition (HCCI) combustion.

When HCCI combustion is performed, the mixture is ignited by the spark plug 14 near the compression top dead center (TDC) during cold start, and part of the fuel in the combustion chamber 10 is burned by flame propagation, and the remaining fuel in the combustion chamber 10, which has become hot due to the combustion, is burned by self-ignition. This type of combustion is referred to below as spark assisted homogeneous charge compression ignition (SAHCCI) combustion.

When fuel is burned in the combustion chamber 10, the pressure in the combustion chamber 10 rises suddenly, and the piston 9 descends (expansion stroke). When the intake port 5 is closed, the exhaust port 6 is opened, and the piston 9 ascends, the air (exhaust) in the combustion chamber 10 is discharged from the exhaust port 6 (exhaust stroke). When the piston 9 reciprocates along the inner wall of the cylinder 2, the crankshaft 18 rotates via the connecting rod 17. The crankshaft 18 of the engine 1 is also provided with a crank angle sensor 19 that detects the rotation angle (crank angle) of the crankshaft 18. A signal indicating the detection result by the crank angle sensor 19 is sent to the ECU 50 (Figure 3).

Gasoline fuel, which is mainly composed of hydrocarbons, can be oxidized and reformed using a catalyst such as N-hydroxyphthalimide (NHPI) to generate peroxides, thereby improving the ignition ability. Specifically, hydrogen atoms of NHPI are easily extracted by oxygen molecules to generate phthalimide-N-oxyl (PINO) radicals. The PINO radicals extract hydrogen atoms from the hydrocarbons (RH) contained in the fuel to generate alkyl radicals (R.). The alkyl radicals combine with oxygen molecules to generate alkylperoxy radicals (ROO.). The alkylperoxy radicals extract hydrogen atoms from the hydrocarbons contained in the fuel to generate alkylhydroperoxides (ROOH), which are peroxides, such as cumene hydroperoxide.

As the oxidation reaction progresses, the peroxide concentration increases, and as the oxidation reaction progresses further, the peroxides are decomposed into oxidants such as alcohols, aldehydes, and ketones, decreasing the peroxide concentration while increasing the oxidant concentration. To increase the peroxide concentration in the fuel and improve the ignition ability of the fuel, it is necessary to adjust the progress of the oxidation reaction to within an appropriate range. Specifically, it is necessary to adjust the peroxide concentration in the reformed fuel to a predetermined concentration or higher so that the octane number of the reformed fuel, which is a part of the gasoline fuel that has been oxidized and reformed, is below a predetermined value.

Figure 2 is a schematic diagram of an example of a fuel supply line 20 that supplies fuel to the engine 1 of the device 100. As shown in Figure 2, the fuel supply line 20 is provided with a fuel tank 21 that stores gasoline fuel, a reformer 22 that oxidizes and reforms the gasoline fuel, a reformed fuel tank 23 that stores the reformed fuel, and a mixer 24 that mixes the gasoline fuel and the reformed fuel. The mixed fuel mixed by the mixer 24 is injected into the combustion chamber 10 of the engine 1 via the injector 13 (Figure 1).

The liquid phase of the fuel tank 21 and the inlet of the reformer 22 are connected via a pipe 25, and the gasoline fuel stored in the fuel tank 21 is supplied to the reformer 22 via the pipe 25 by an electric pump 26 provided on the pipe 25. The operation of the electric pump 26 is controlled by the ECU 50 (Figure 3).

The reformer 22 is filled with a catalyst such as NHPI. The reformer 22 is provided with a heater 27 that adjusts the temperature of the reformer 22, and oxidizes and reforms a portion of the gasoline fuel supplied from the fuel tank 21 into peroxides at a reforming rate according to the temperature. The reformed fuel after oxidative reforming contains peroxides such as cumene hydroperoxide at a rate according to the reforming rate. The operation of the heater 27 is controlled by the ECU 50 (Figure 3).

The outlet of the reformer 22 and the reformed fuel tank 23 are connected via a pipe 28. The reformed fuel reformed by the reformer 22 is supplied to the reformed fuel tank 23 via the pipe 28. A condenser 29 is provided in the pipe 28 between the reformer 22 and the reformed fuel tank 23. The gaseous fuel after reforming is condensed in the condenser 29 and stored as a liquid in the reformed fuel tank 23. The reformed fuel tank 23 is provided with a concentration sensor 23a, for example of a capacitance type, which detects the peroxide concentration C1 of the reformed fuel stored as a liquid in the reformed fuel tank 23. A signal indicating the detection result by the concentration sensor 23a is sent to the ECU 50 (Figure 3).

The liquid phase of the fuel tank 21 is further connected to the mixer 24 via a pipe 30. The gasoline fuel stored in the fuel tank 21 is supplied to the mixer 24 via the pipe 30 by an electric pump 31 provided in the pipe 30. The liquid phase of the reformed fuel tank 23 is connected to the mixer 24 via a pipe 32. The reformed fuel stored in the reformed fuel tank 23 is supplied to the mixer 24 via the pipe 32 by an electric pump 33 provided in the pipe 32. The operation of the electric pumps 31 and 33 is controlled by the ECU 50 (Figure 3). The mixer 24 is provided with a concentration sensor 24a, for example of a capacitance type, which detects the peroxide concentration C2 of the mixed fuel. A signal indicating the detection result by the concentration sensor 24a is sent to the ECU 50 (Figure 3).

Figure 3 is a block diagram showing an example of the main configuration of device 100. As shown in Figure 3, device 100 is mainly composed of ECU 50, which includes a computer having a processing unit 51 such as a CPU, a storage unit 52 such as ROM and RAM, and other peripheral circuits (not shown) such as an I/O interface. ECU 50 may be configured as part of an engine control ECU that controls the operation of engine 1.

The ECU 50 is electrically connected to the water temperature sensor 15, the outside air temperature sensor 16, the crank angle sensor 19, and the concentration sensors 23a and 24a, and receives signals from each of these sensors. The ECU 50 is also electrically connected to the actuators of the throttle valve 12, the injector 13, the spark plug 14, the electric pumps 26, 31, and 33, and the heater 27, and transmits control signals from the ECU 50 to each of the actuators.

The ECU 50 controls the opening of the throttle valve 12, the fuel injection timing and fuel injection amount of the injector 13, the ignition timing of the spark plug 14, and the on/off of ignition by the spark plug 14, etc., according to the operating conditions of the engine 1, such as the engine speed and required torque. The target opening of the throttle valve 12, the target fuel injection timing and target fuel injection amount of the injector 13, the target ignition timing of the spark plug 14, etc. are determined in advance according to the operating conditions of the engine 1 and stored in the memory unit 52 of the ECU 50 as a characteristic map, etc. In addition, the ECU 50 controls the electric pump 26 and the heater 27 so that the peroxide concentration C1 of the reformed fuel detected by the concentration sensor 23a is equal to or higher than a predetermined concentration corresponding to a predetermined octane number. As a result, the reformed fuel tank 23 stores reformed fuel whose peroxide concentration C1 is equal to or higher than a predetermined concentration and whose octane number is equal to or lower than a predetermined value.

Figure 4 is a diagram for explaining the relationship between the peroxide concentration C2 in the fuel supplied to the engine 1 and the octane number and ignition quality. As shown in Figure 4, the higher the peroxide concentration C2, the lower the octane number and the higher the ignition quality.

Figure 5 is a diagram for explaining the relationship between the fuel injection timing and the in-cylinder temperature and heat release rate, and shows the calculation results when the mixture is compressed under normal pressure and low temperature (-30°C) conditions. As shown in Figure 5, with gasoline fuel, no sudden rise in the in-cylinder temperature due to fuel ignition was observed whether the intake stroke injection was performed with fuel injected at a crank angle of -180 degrees based on the compression top dead center (TDC), or whether the compression stroke injection was performed with fuel injected at -30 degrees. In addition, whether the intake stroke injection was performed or the compression stroke injection was performed, almost no heat was observed near the compression top dead center (TDC), and it was confirmed that the low-temperature oxidation reaction, which is an exothermic reaction caused by a slow oxidation reaction of fuel molecules, was hardly progressing.

On the other hand, when reformed fuel was injected during the compression stroke, a rapid temperature rise due to ignition was observed near the compression top dead center (TDC). In addition, whether the fuel was injected during the intake stroke or the compression stroke, heat was generated near the compression top dead center (TDC), confirming that a low-temperature oxidation reaction was progressing. When the fuel was injected during the compression stroke, a rapid rise in the heat generation rate was observed near the compression top dead center (TDC), confirming that in addition to the low-temperature oxidation reaction, a combustion reaction had begun.

Figure 6 is a diagram for explaining the relationship between the fuel injection timing and the in-cylinder pressure and heat release rate, and shows the change in the in-cylinder pressure and heat release rate when reformed fuel is injected under the condition of an intake pressure of 130 kPa. As shown in Figure 6, when fuel is injected during the compression stroke at -30 degrees, a sudden rise in the in-cylinder pressure due to ignition was observed near the compression top dead center (TDC). When the injection timing is retarded and fuel is injected in the latter half of the compression stroke, the air in the cylinder is compressed and the fuel is injected at a high in-cylinder temperature, and the fuel distribution in the cylinder becomes uneven, so that the low-temperature oxidation reaction proceeds sufficiently and the in-cylinder temperature can be raised to a temperature at which self-ignition occurs.

When starting the engine 1, the ECU 50 determines whether or not the engine is in a cold start state based on the water temperature Tw detected by the water temperature sensor 15 and the outside air temperature Ta detected by the outside air temperature sensor 16. More specifically, when the water temperature Tw is equal to or lower than a first predetermined water temperature Tw1 and the outside air temperature Ta is equal to or lower than a predetermined outside air temperature Ta1, the ECU 50 determines that the engine is in a cold start state, and when the water temperature Tw exceeds the first predetermined water temperature Tw1 or the outside air temperature Ta exceeds the predetermined outside air temperature Ta1, the ECU 50 determines that the engine is in a normal start state. The first predetermined water temperature Tw1 is the water temperature Tw at the time of cold start, and the predetermined outside air temperature Ta1 is the outside air temperature Ta at the time of cold start.

When the ECU 50 determines that the engine is in a normal start state, it controls the electric pumps 31, 33 and the injector 13 to inject gasoline fuel at the normal target injection timing (hereinafter, the first target injection timing). More specifically, it turns off the electric pump 33 and turns on the electric pump 31 to introduce the gasoline fuel stored in the fuel tank 21 directly to the injector 13 and controls the injector 13 to inject gasoline fuel at the first target injection timing.

When the ECU 50 determines that the engine is in a cold start state, it controls the electric pumps 31, 33 and the injector 13 to inject the reformed fuel at a second target injection time that is retarded from the first target injection time. More specifically, it turns off the electric pump 31 and turns on the electric pump 33 to introduce the reformed fuel stored in the reformed fuel tank 23 to the injector 13 and controls the injector 13 to inject gasoline fuel at the second target injection time. If the remaining amount of reformed fuel stored in the reformed fuel tank 23 is insufficient, the electric pump 31 may be turned on in addition to the electric pump 33 to introduce a mixture of gasoline fuel and reformed fuel to the injector 13.

Figure 7 is a diagram for explaining the injection timing during cold start, and shows an example of a characteristic map of the retard amount of the second target injection timing relative to the first target injection timing. As shown in Figure 7, the retard amount of the second target injection timing relative to the first target injection timing is set to the retard side as the water temperature Tw of the engine 1 is lower and the peroxide concentration C2 in the fuel supplied to the engine 1 is lower. Such a characteristic map is set in advance and stored in the memory unit 52 of the ECU 50. The ECU 50 (processing unit 51) calculates the retard amount by referring to the characteristic map stored in the memory unit 52 based on the water temperature Tw detected by the water temperature sensor 15 and the peroxide concentration C2 detected by the concentration sensor 24a, and calculates the second target injection timing.

For engine 1 that uses gasoline fuel during normal operation, starting performance can be improved by retarding the injection timing during cold start compared to normal, and injecting highly ignitable reformed fuel into the combustion chamber 10 where the intake air has been compressed and the temperature has become relatively high.

When the engine 1 is configured as a homogeneous charge compression ignition engine, the ECU 50, upon determining that the engine is cold started, controls the spark plug 14 to ignite the mixture of the reformed fuel and air in the combustion chamber 10 in addition to supplying the reformed fuel and retarding the injection timing as described above. In other words, the engine 1 is controlled to perform SAHCCI combustion.

After supplying the reformed fuel, retarding the injection timing, and performing SAHCCI combustion as described above, the ECU 50 determines whether ignition by the spark plug 14 was successful in a predetermined number of combustion cycles, for example based on the fluctuation in the crank angle detected by the crank angle sensor 19. When the ECU 50 determines that ignition was successful in a predetermined number of combustion cycles and the engine 1 has been started reliably, it ends the supply of reformed fuel and retards the injection timing, and controls the electric pumps 31, 33 and the injector 13 to inject gasoline fuel at the first target injection timing. After the engine 1 has been started reliably, the thermal efficiency of the engine 1 can be improved by switching to gasoline fuel injection at the normal ignition timing.

When the engine 1 is a homogeneous charge compression ignition engine, the ECU 50 controls the spark plug 14 to stop ignition on the condition that the water temperature Tw exceeds a second predetermined water temperature Tw2 that is higher than the first predetermined water temperature Tw1. When the water temperature Tw exceeds the second predetermined water temperature Tw2 and the in-cylinder temperature exceeds a predetermined temperature, the possibility of knocking occurring increases if SAHCCI combustion accompanied by ignition is continued. The second predetermined water temperature Tw2 is a water temperature Tw corresponding to a predetermined in-cylinder temperature at which the possibility of knocking increases. When the water temperature Tw exceeds the second predetermined water temperature Tw2, ignition is terminated and SAHCCI combustion is switched to HCCI combustion with high thermal efficiency, thereby reducing the possibility of knocking and further improving the thermal efficiency of the engine 1.

Figure 8 is a flow chart showing an example of a start process when the device 100 is applied to a spark ignition engine, and shows an example of the start process executed by the ECU 50 (processing unit 51) of Figure 3. The start process of Figure 8 is executed when the engine 1 is started. As shown in Figure 8, first, in step S1, signals from each sensor are read and it is determined whether the water temperature Tw is equal to or lower than a first predetermined water temperature Tw1 and whether the outside air temperature Ta is equal to or lower than a predetermined outside air temperature Ta1. If the result in step S1 is positive, it is determined to be a cold start and the process proceeds to step S2. If the result in step S1 is negative, it is determined to be a normal start and the process proceeds to step S4.

In step S2, the electric pumps 31, 33 and the injector 13 are controlled to inject reformed fuel at the second target injection timing. Next, in step S3, it is determined whether ignition by the spark plug 14 has been successful for a predetermined number of combustion cycles. If the result in step S3 is negative, the process returns to step S2, and the supply of reformed fuel and the retardation of the injection timing are continued. If the result in step S3 is positive, the process proceeds to step S4. In step S4, the electric pumps 31, 33 and the injector 13 are controlled to inject gasoline fuel at the first target injection timing.

Figure 9 is a flow chart showing an example of a start process when the device 100 is applied to a homogenous charge compression ignition engine, and shows an example of the start process executed by the ECU 50 (processing unit 51) of Figure 3. The start process of Figure 9 is executed when the engine 1 is started. As shown in Figure 9, first, in step S10, signals from each sensor are read and it is determined whether the water temperature Tw is equal to or lower than a first predetermined water temperature Tw1 and whether the outside air temperature Ta is equal to or lower than a predetermined outside air temperature Ta1. If the result in step S10 is positive, it is determined that the start is a cold start, and the process proceeds to step S11. If the result in step S10 is negative, it is determined that the start is a normal start, and the process proceeds to step S14.

In step S11, the electric pumps 31, 33 and the injector 13 are controlled to inject the reformed fuel at the second target injection timing, and the spark plug 14 is controlled to ignite the mixture of the reformed fuel and air in the combustion chamber 10. That is, the engine 1 is controlled to perform SAHCCI combustion using the reformed fuel. Next, in step S12, it is determined whether ignition by the spark plug 14 has been successful for a predetermined number of combustion cycles. If the result in step S12 is negative, the process returns to step S11 and SAHCCI combustion using the reformed fuel continues. If the result in step S12 is positive, the process proceeds to step S13.

In step S13, the electric pumps 31, 33 and the injector 13 are controlled to inject gasoline fuel at the first target injection timing, and the spark plug 14 is controlled to ignite the mixture of gasoline fuel and air in the combustion chamber 10. That is, the engine 1 is controlled to perform SAHCCI combustion using gasoline fuel. Next, in step S14, it is determined whether the water temperature Tw exceeds the second predetermined water temperature Tw2. If the result in step S14 is negative, the process returns to step S13, and SAHCCI combustion using gasoline fuel is continued. If the result in step S14 is positive, the process proceeds to step S15, and the engine 1 (spark plug 14) is controlled to stop ignition and switch from SAHCCI combustion using gasoline fuel to HCCI combustion using gasoline fuel.

According to this embodiment, the following advantageous effects can be obtained.
(1) The device 100 includes an engine 1 having an injector 13 that injects fuel into a combustion chamber 10 and an ignition plug 14 that ignites a mixture of fuel and air in the combustion chamber 10, a water temperature sensor 15 that detects a water temperature Tw of the engine 1, and an ECU 50 that controls the injector 13 based on the water temperature Tw detected by the water temperature sensor 15 (FIGS. 1 and 3). The fuel injected from the injector 13 is at least one of gasoline fuel and reformed fuel obtained by reforming a part of the gasoline fuel into a peroxide (FIG. 2).

When the water temperature Tw detected by the water temperature sensor 15 exceeds a first predetermined water temperature Tw1 at the start of the engine 1, the ECU 50 controls the injector 13 to inject gasoline fuel at a first target injection timing, and when the water temperature Tw detected by the water temperature sensor 15 is equal to or lower than the first predetermined water temperature Tw1, the ECU 50 controls the injector 13 to inject reformed fuel at a second target injection timing that is retarded from the first target injection timing (steps S1, S2, and S4 in FIG. 8; steps S10, S11, and S13 in FIG. 9). For the engine 1 that uses gasoline fuel during normal operation, the injection timing is retarded from normal at cold start, and highly ignitable reformed fuel is injected into the combustion chamber 10 where the intake air is compressed and becomes relatively hot, thereby improving startability.

(2) Engine 1 is a spark ignition engine, and the first predetermined water temperature Tw1 is the water temperature Tw at the time of cold start of engine 1. After controlling injector 13 to inject reformed fuel at the second target injection timing, if ignition by spark plug 14 is successful in a predetermined number of combustion cycles, ECU 50 controls injector 13 to inject gasoline fuel at the first target injection timing (steps S3 and S4 in FIG. 8). After engine 1 has been started reliably, the thermal efficiency of engine 1 can be improved by switching to gasoline fuel injection at the normal ignition timing.

(3) The engine 1 is a homogenous charge compression ignition engine. When the water temperature Tw detected by the water temperature sensor 15 is equal to or lower than the first predetermined water temperature Tw1, the ECU 50 controls the spark plug 14 to ignite the mixture of the reformed fuel and air in the combustion chamber 10 (steps S10 and S11 in FIG. 9). During cold start of a homogenous charge compression ignition engine, starting performance can be further improved by switching to SAHCCI combustion, which supplies reformed fuel, retards the injection timing, and also performs ignition.

(4) The first predetermined water temperature Tw1 is the water temperature Tw at the time of cold start of the engine 1. The ECU 50 controls the injector 13 to inject reformed fuel at the second target injection timing, controls the spark plug 14 to ignite the mixture of reformed fuel and air in the combustion chamber 10, and then, if ignition by the spark plug 14 is successful in a predetermined number of combustion cycles, controls the injector 13 to inject gasoline fuel at the first target injection timing and controls the spark plug 14 to ignite the mixture of gasoline fuel and air in the combustion chamber 10 (steps S11 to S13 in FIG. 9). After the engine 1 has been started reliably, the thermal efficiency of the engine 1 can be improved by switching to gasoline fuel injection at the normal ignition timing.

(5) When ignition by the spark plug 14 is successful in a predetermined number of combustion cycles, the ECU 50 controls the spark plug 14 to stop ignition on the condition that the water temperature Tw detected by the water temperature sensor 15 exceeds a second predetermined water temperature Tw2 that is higher than the first predetermined water temperature Tw1 (steps S14 and S15 in FIG. 9). When the water temperature Tw exceeds the second predetermined water temperature Tw2, ignition is terminated and the combustion is switched from SAHCCI combustion to HCCI combustion, which has higher thermal efficiency, thereby reducing the possibility of knocking and further improving the thermal efficiency of the engine 1.

In the above embodiment, the engine 1 is described as a spark ignition engine and a homogeneous charge compression ignition engine, but the engine having an injector and a spark plug is not limited to these. For example, the engine may be one that switches between multiple combustion modes, including SI combustion and HCCI combustion, depending on the operating conditions.

In the above embodiment, the internal configuration of the engine 1 is illustrated in FIG. 1 and other figures, but the internal configuration of the engine, such as the arrangement of the injectors and spark plugs, is not limited to what is shown.

In the above embodiment, an example was described in which reformed fuel reformed on-board by a reformer 22 mounted on the vehicle was used, but the reformed fuel in which part of the gasoline fuel is reformed into peroxide is not limited to this. For example, it may be reformed fuel that has been produced in advance and stored in an on-board fuel tank.

In the above embodiment, an example has been described in Figs. 2, 3, etc. in which reformed fuel is stored in the reformed fuel tank 23, and the ECU 50 controls the electric pump 33 and the injector 13 to supply the reformed fuel to the engine 1, but the control unit that controls the injector is not limited to this. For example, the electric pump 26 and heater 27 may be controlled instead of the electric pump 33, and the reformer 22 may be switched on and off, or the reforming rate and amount of reforming by the reformer 22 may be adjusted, thereby supplying the reformed fuel to the engine 1. In this case, the reformed fuel tank 23 and the electric pump 33 may not be provided.

In the above embodiment, an example is described in FIG. 2 etc. in which a mixer 24 is provided to mix gasoline fuel and reformed fuel, but if a sufficient amount of reformed fuel can be supplied, the mixer 24 does not need to be provided.

In the above embodiment, an example is described in which it is determined whether or not the engine is in a cold start state based on the water temperature Tw and the outside air temperature Ta in FIG. 8, FIG. 9, etc., but the control unit that controls the injector based on the engine temperature is not limited to this. For example, it may be determined whether or not the engine is in a cold start state based only on the water temperature Tw.

The above description is merely an example, and the present invention is not limited to the above-mentioned embodiment and modifications, as long as the characteristics of the present invention are not impaired. It is also possible to arbitrarily combine one or more of the above-mentioned embodiment and modifications, and it is also possible to combine modifications together.

1 engine, 10 combustion chamber, 13 injector, 14 spark plug, 15 water temperature sensor, 16 outside air temperature sensor, 19 crank angle sensor, 20 fuel supply line, 21 fuel tank, 22 reformer, 23 reformed fuel tank, 23a, 24a concentration sensor, 24 mixer, 26, 31, 33 electric pump, 27 heater, 50 ECU, 51 processing unit, 52 memory unit, 100 engine control device (device)

Claims (3)

an engine that is a spark ignition engine having an injector that injects fuel into a combustion chamber and an ignition plug that ignites a mixture of fuel and air in the combustion chamber;
a temperature detection unit for detecting a cooling water temperature of the engine;
a control unit that controls the injector based on the cooling water temperature detected by the temperature detection unit,
The fuel injected from the injector is at least one of gasoline fuel and reformed fuel obtained by reforming a part of the gasoline fuel into a peroxide,
The control unit controls the injector to inject the gasoline fuel at a first target injection time when the cooling water temperature detected by the temperature detection unit exceeds a predetermined temperature, which is the cooling water temperature at a cold start of the engine, when the engine is started, and controls the injector to inject the reformed fuel at a second target injection time that is retarded from the first target injection time when the cooling water temperature detected by the temperature detection unit is below the predetermined temperature, and thereafter, when ignition by the spark plug is successful in a predetermined number of combustion cycles, controls the injector to inject the gasoline fuel at the first target injection time . An engine that is a homogeneous charge compression ignition engine having an injector that injects fuel into a combustion chamber and an ignition plug that ignites a mixture of fuel and air in the combustion chamber;
a temperature detection unit for detecting a cooling water temperature of the engine;
a control unit that controls the injector and the spark plug based on the cooling water temperature detected by the temperature detection unit,
The fuel injected from the injector is at least one of gasoline fuel and reformed fuel obtained by reforming a part of the gasoline fuel into a peroxide,
The control unit controls the injector to inject the gasoline fuel at a first target injection time when the cooling water temperature detected by the temperature detection unit exceeds a predetermined temperature, which is the cooling water temperature at a cold start of the engine, when the engine is started, and controls the injector to inject the reformed fuel at a second target injection time that is retarded from the first target injection time when the cooling water temperature detected by the temperature detection unit is below the predetermined temperature, and controls the spark plug to ignite the mixture of the reformed fuel and air in the combustion chamber, and thereafter, when ignition by the spark plug is successful for a predetermined number of combustion cycles, controls the injector to inject the gasoline fuel at the first target injection time, and controls the spark plug to ignite the mixture of the gasoline fuel and air in the combustion chamber. 3. The engine control device according to claim 2,
the predetermined temperature is a first predetermined temperature,
The control unit controls the spark plug to stop ignition when ignition by the spark plug is successful in the specified number of combustion cycles, on the condition that the cooling water temperature detected by the temperature detection unit exceeds a second specified temperature that is higher than the first specified temperature.

Images